NANO130: Decrease heap to 3.75KiB to spare SRAM for static allocation

This adjustment is to pass compile on IAR for adding logging and statistics configuration.

Author: ccli8

targets/TARGET_NUVOTON/TARGET_NANO100/device/TOOLCHAIN_IAR/NANO130.icf

@@ -11,7 +11,7 @@ define symbol __ICFEDIT_region_IRAM_start__ = 0x20000000;
 define symbol __ICFEDIT_region_IRAM_end__   = 0x20004000 - 1;
 /*-Sizes-*/
 define symbol __ICFEDIT_size_cstack__ = MBED_BOOT_STACK_SIZE;
-define symbol __ICFEDIT_size_heap__   = 0xC00;
+define symbol __ICFEDIT_size_heap__   = 0xB00;
 /**** End of ICF editor section. ###ICF###*/